SPECTATOR: Perfusion Monitoring Before, During and After Lower Extremity Revascularization With Laser Speckle Contrast Imaging

Rationale: Lower extremity arterial disease (LEAD) arises from atherosclerotic obstruction in the lower limbs, which in turn leads to symptoms ranging from intermittent claudication to ulcer formation. As the disease progresses, patients often require revascularization to achieve limb salvage.

To improve prediction of clinical outcomes following revascularization, various techniques have been introduced to quantify tissue perfusion. Among these, near-infrared fluorescence imaging with indocyanine green (ICG NIRF) has gained attention. This method combines a laser light source with intravenous ICG administration to visualize perfusion. Although ICG NIRF appears promising for guiding revascularization strategies and predicting outcomes, its invasive nature, requiring dye injection, limits its use in outpatient settings.

Consequently, there is a need for a non-invasive, real-time technique that enables rapid and straightforward perfusion assessment. One such promising approach is laser speckle contrast imaging (LSCI). Therefore, this study aims to evaluate the feasibility of LSCI for perioperative perfusion assessment of the lower extremity before, during, and after revascularization.

Objective:The primary objective of this study is to evaluate the feasibility of laser speckle contrast imaging (LSCI) for monitoring perfusion in the lower extremities during and following revascularization.

Secondary objectives include correlating LSCI findings with the temperature of the patient's foot, comparing LSCI with near-infrared fluorescence imaging using indocyanine green (ICG NIRF) and exploring potential quantitative approaches such as the assessment of blood flow pulsatility.

Study design: This study will be a prospective cohort study. Study population: Adult patients undergoing a revascularization of the lower extremity due to peripheral artery disease. Such revascularization can be bypass surgery, thrombo-endarterectomy (TEA), or endovascular percutaneous transluminal angioplasty (PTA).

Intervention: Patients will undergo peri-operative and post-operative LSCI.

Main study parameters/endpoints: The main study parameters are the quantified perfusion parameters measured with LSCI.

Nature and extent of the burden and risks associated with participation. The use of the LSCI device is not expected to cause any adverse effects, as it employs a low-intensity near-infrared laser to illuminate the skin. The photon energy and illumination power used are well below levels that could cause tissue damage and are therefore considered safe for human skin. All measurements are performed alongside standard assessments or routine outpatient clinic appointments. The intraoperative measurement does not extend the duration of the surgical procedure. Given the short duration of each measurement (5-10 seconds), no additional burden on patients is anticipated.

• Correlation of pre-, intra- and postsurgery laser speckle contrast imaging (LSCI) findings with the pre-, intra- and post-temperature of the patient's foot [Time frame: 2 years]
• Comparative analysis of LSCI with standard of care near-infrared fluorescence imaging using ICG [Time frame: 2 years]
• Exploration of quantitative approaches to LSCI analysis, including assessment of blood flow pulsatility [Time frame: 2 years]
• Correlation of quantified LSCI recordings to clinical outcomes. [Time frame: 2 years]